This invention relates to a process for decorating glass or ceramic articles, to a printing apparatus for decorating glass or ceramic articles to a glass frit formulation, to a pigment formulation, to a combination of a glass frit formulation and of a pigment formulation, to a decorated glass or ceramic article, and also to a transfer medium for use in decorating a glass or ceramic article.
U.S. Pat. No. 6,694,885 B2 discloses a process for preparing a ceramic decal wherein a transfer medium has initially applied to it a flux layer by means of adhesives and then a color image is printed onto the flux layer by means of a thermal transfer printing process. Disposed above the color image is a flux protective layer. Optionally, an opacification layer and also a further flux-adhesive layer may be applied underneath the color image layer. Owing to the use of a thermal transfer printer, the composition of the layers to be applied has to meet special requirements. For example, the flux layers have to contain wax compounds. Thermal transfer printing is comparatively tricky to handle, inter alia owing to the necessary use of ink ribbons.
JP 2004-99432 A discloses a process wherein a substrate has initially applied to it a glass frit layer and the glass frit layer is then printed with a pigment layer by means of an inkjet printer, whereupon the substrate with the two layers is heated, i.e., fired, to melt the glass frit layer. Owing to the provision of the lower glass frit layer, good adherence of the printed image layer to the substrate is ensured. One disadvantage with the existing process is that the final product leaves something to be desired in terms of gloss/luster and surface finish.
This invention therefore has for its object to propose a process for decorating glass or ceramic articles whereby high-quality, in particular high-definition, decorations having a lustrous and smooth surface are obtainable. More particularly, the process shall be economical to use with small as well as large batches. The object further consists in proposing a printing apparatus for decorating glass or ceramic articles whereby glass or ceramic articles can be decorated to a high standard. More particularly, the printing apparatus shall enable small as well as large batches to be decorated economically. It is a further object to propose a glass frit formulation and also a pigment formulation for a high-quality decoration of glass or ceramic articles that are suitable for being applied by printing in an inkjet printing operation. It is a further object to propose a decorated glass or ceramic article and also a transfer medium which is useful in the decoration of glass or ceramic articles.